1. Field of the Invention
The present invention relates to a technique of performing still image capturing without stopping moving image recording in an apparatus which performs still image capturing during moving image recording.
2. Description of the Related Art
Recently, a digital still camera or digital video camera aimed at still image capturing during moving image recording has been proposed. For example, Japanese Patent Laid-Open No. 9-233410 discloses a digital video camera which can write still image data in a recording medium upon completion of moving image recording by temporarily storing the data in a memory in advance, when a request to perform still image capturing is issued during the moving image recording.
The technique disclosed in Japanese Patent Laid-Open No. 9-233410, however, suffers from a problem that it is not possible to record a high resolution still image because the recording size of the still image is not associated with the size of images output from a solid-state image sensor and a one-frame image in moving image recording is recorded.
In contrast, Japanese Patent Laid-Open No. 2006-310907 has proposed a digital camera designed to temporarily stop moving image recording upon performing still image capturing and resume the moving image recording as a method of recording a still image with high resolution during moving image recording. This patent literature describes a technique of recording a moving image without skipping any missing frame by inserting a black image in each missing frame.
The technique disclosed in Japanese Patent Laid-Open No. 2006-310907 has, however, a problem that since there are missing frames, the user cannot see anything that has occurred during each missing frame at the time of moving image reproduction.
One of the reasons why it is not possible to capture a high resolution still image without stopping moving image capturing during moving image recording is that moving image processing occupies a development processing circuit, and the circuit cannot be used for a still image development process. However, respectively having development process circuits for moving images and still images will hinder the reduction of cost, size, and power consumption. That is, this is not a preferable solution.
Recently, an increase in the operation speed of an image sensor or dedicated signal processing IC has been enabling to read out a high resolution moving image with the number of pixels similar to that of a still image. This makes it possible to temporarily store high resolution still image RAW data in a memory in advance without stopping moving image capturing during moving image recording and write the data in a recording medium upon completion of moving image recording.
However, the memory occupation of high resolution still image RAW data is very large. On the other hand, since the capacity of a memory which can temporarily store data is limited, the number of frames of still images which can be recorded during moving image recording is considerably limited by the memory capacity.
FIG. 12 is a timing chart for schematically explaining the above operation. Referring to FIG. 12, when starting still image capturing during moving image recording, the image capturing apparatus sequentially stores still image RAW data in predetermined areas like the memory 1 area and the memory 2 area of the semiconductor memory in the apparatus for every operation. This will soon fill the capacity of the semiconductor memory. The still image RAW data stored in the semiconductor memory is developed and recorded after the completion of moving image capturing, the capacity of the semiconductor memory becomes full at the Nth frame in the case shown in FIG. 12. Thereafter, it is not possible to perform still image capturing until the end of moving image capturing.